//https://leetcode.cn/problems/number-of-enclaves/

class Solution {
    int dx[4] = { 0,0,-1,1 };
    int dy[4] = { -1,1,0,0 };
public:
    int numEnclaves(vector<vector<int>>& grid) {

        int m = grid.size(), n = grid[0].size();
        vector<vector<int>> vit(m, vector<int>(n, -1));
        queue<pair<int, int>> q;

        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (i == 0 || i == m - 1 || j == 0 || j == n - 1)
                {
                    if (grid[i][j])
                    {
                        q.push({ i,j });
                        vit[i][j] = 1;
                    }
                }
            }
        }

        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();

            for (int i = 0; i < 4; i++)
            {
                int x = a + dx[i];
                int y = b + dy[i];
                if (x >= 0 && x < m && y >= 0 && y < n && vit[x][y] == -1 && grid[x][y] == 1)
                {
                    q.push({ x,y });
                    vit[x][y] = 1;
                }
            }
        }

        int ret = 0;
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (grid[i][j] == 1 && vit[i][j] == -1)
                {
                    ret++;
                }
            }
        }

        return ret;

    }
};